In order to keep food, drugs, electronic members, and electronic devices from deteriorating and spoiling due to oxygen, water vapor, or the like, gas barrier materials, such as a gas barrier film that suppresses the permeability to oxygen or water vapor, are used for packaging the above.
In the related art, as examples of barrier materials, a copolymer of polyvinyl alcohol (PVA) and ethylene vinyl alcohol, resin films, such as polyvinylidene chloride resin, films on which these resins are coated, ceramic vapor deposition films, and the like are used, and laminated bodies in which the gas barrier material is laminated on various bases are being studied.
Additionally, many molded containers made of plastics or the like are used as barrier containers. However, plastics are mostly limited resources originating from petroleum and have high combustion heat, and environmental problems or the like. With recent environmental preservation type thinking or enforcement of the Container and Packaging Recycling Law, converting from plastic materials to renewable materials originating from natural resources, such as paper, is needed.
In addition, the study of providing various barrier layers on paper and utilizing the resulting products as packaging materials has been performed. For example, a technique of bonding a paper base to a film having barrier properties or a film having a barrier layer, a technique (for example, refer to PTL 1) of providing a resin composite layer having an inorganic layered compound or a thermoplastic resin layer on a paper base, or a technique of providing a resin layer on a paper base or a paper container and laminating an inorganic thin film layer through vapor deposition, CVD, or the like to thereby give barrier properties has been studied.
However, countless irregularities are present in the surface of the paper base in the order of millimeters or nanometers. Therefore, in the technique of laminating an inorganic thin film layer on a paper base to thereby give barrier properties, in a case where an inorganic thin film layer having a glassy property and an extremely brittle property is formed as a film, problems have been pointed out that defects resulting from being formed on irregularities of the surface of the paper base are generated within the barrier layer, and barrier properties are degraded.
Additionally, when various barrier layers are provided on paper to give barrier properties, it is considered that the density, air permeability, or smoothness of the paper base is controlled to give higher barrier properties. For example, a technique of using paper with a high density or filling resin between paper fibers has been studied.
However, these techniques are techniques that cannot give sufficient barrier properties or that perform contact or bonding only and have little interaction with the paper fibers. Additionally, even in the technique of performing filling through coating, impregnation, or the like, a layer that follows irregularities in the order of millimeters or nanometers on the paper surface, may be formed, and a sufficient function cannot be exhibited. Therefore, a layer having a considerable thickness had to be formed to remove influence of the irregularities of the paper, and was a mere filling and plugging material.
Additionally, since many of such fillers use synthetic polymers originating from petroleum, the fillers cannot sufficiently utilize the advantages of renewable materials originating from natural products that a paper material intrinsically has. In addition, although some fillers made of materials originating from natural products and obtained through coating or the like of polymers or fibers having barrier properties, have also been reported, in a mere polymer in which molecules are dispersed, the layer that follows the irregularities on the surface of the paper will be formed due to the form and softness of the polymer. Additionally, a film that has functions in the form of a thin film is not obtained, and even if the layer having considerable thickness is formed, those in which both the aforementioned barrier and filling functions and environmental friendliness are sufficiently achieved are not obtained.